Props Validation - ReactJS

Properties validation is a useful way to force the correct usage of the components. This will help during development to avoid future bugs and problems, once the app becomes larger. It also makes the code more readable, since we can see how each component should be used.

Validating Props

In this example, we are creating App component with all the props that we need. App.propTypes is used for props validation. If some of the props aren't using the correct type that we assigned, we will get a console warning. After we specify validation patterns, we will set App.defaultProps.


import PropTypes from 'prop-types';
import React from 'react';
import ReactDOM from 'react-dom';

class App extends React.Component {
   render() {
      return ( 
            <h1> Hello, {} </h1>
            <h3>Array: {this.props.propArray}</h3>			
            <h3>Bool: {this.props.propBool ? "True..." : "False..."}</h3>
            <h3>Func: {this.props.propFunc(3)}</h3>
            <h3>Number: {this.props.propNumber}</h3>
            <h3>String: {this.props.propString}</h3>
App.propTypes = {
   name: PropTypes.string,
   propArray: PropTypes.array.isRequired,
   propBool: PropTypes.bool.isRequired,
   propFunc: PropTypes.func,
   propNumber: PropTypes.number,
   propString: PropTypes.string,
App.defaultProps = {
   name: '',
   propArray: [1, 2, 3, 4, 5],
   propBool: true,
   propFunc: function(e) {
      return e
   propNumber: 1,
   propString: "String value..."
export default App;


import React from 'react';
import PropTypes from 'prop-types';
import ReactDOM from 'react-dom';
import App from './App.jsx';

ReactDOM.render(<App/>, document.getElementById('app'));


var config = {
   entry: './main.js',
   output: {
      filename: 'index.js',
   devServer: {
      inline: true,
      port: 8080
   externals: {
      'react': 'React'
   module: {
      loaders: [
            test: /\.jsx?$/,
            exclude: /node_modules/,
            loader: 'babel-loader',
            query: {
               presets: ['es2015', 'react']
module.exports = config;

Since all props are valid, we will get the following result.

As can be noticed, we have use isRequired when validating propArray and propBool. This will give us an error, if one of those two don't exist. If we delete propArray: [1,2,3,4,5] from the App.defaultProps object, the console will log a warning.


If we set the value of propArray: 1, React will warn us that the propType validation has failed, since we need an array and we got a number.


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